As the number of connected objects increases, there is a need to propose solutions that exploit the possibilities the Web offers to facilitate communication between physical objects and make rich user interaction a reality. Our work relies on the notion of avatar, designed to extend an object on the Web. An avatar provides an entry point to the object it extends, as well as additional intelligence via internal reasoning and interaction with other avatars and external Web resources. We herein propose a model for the reasoning part of the avatar, to expose semantic, high-level behaviors (aka functionalities) on the Web, based on capabilities that available objects offer. We motivate our work with a temperature regulation scenario, before presenting our model and the reasoning mechanisms put into play in this context, and we evaluate the applicability of our proposal with an implementation.